Renewable fuel/lubricant mixture for use in a two-stroke internal combustion engine

ABSTRACT

A method is provided, which includes operating a two-stroke engine with a lubricating fuel, the lubricating fuel including at least one fuel selected from the group including C 1-6  alcohol, gasoline, ether, ketone, nitromethane, and a mixture thereof, and at least one lubricant selected from the group including biodiesel, lipid, fatty acid alkyl ester, fatty acid, and a mixture thereof. Lubricating fuel compositions are also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on, and claims priority to, U.S. Provisional Application Ser. No. 60/660,330, filed Mar. 11, 2005, the entire contents of which are hereby incorporated by reference.

BACKGROUND

1. Field

The invention relates to lubricating fuels, their preparation, and their use.

2. Discussion of the Background

A wide variety of equipment is powered by two-stroke internal combustion engines such as leaf blowers, string trimmers, outboard motors, watercraft, motorcycles, chain saws, lawnmowers, snowmobiles, etc. The main reason for their wide application is their high ratio of horsepower to weight. The reason for the increased horsepower is that two-stroke motors ignite on every stroke of the engine unlike four-stroke engines that ignite fuel every other stroke. Another advantage to two-stroke engines over four-stroke engines is 2-stroke engines require less valves and as a consequence are much simpler and cheaper to manufacture. Although two-stroke and four-stroke engines burn traditional gasoline fuel, two-stroke engine operation requires the addition of a lubricant in the fuel in ratios of 40:1 or 50:1 to reduce friction thereby preventing damage to the cylinder, piston, and rings resulting from overheating.

Two-stroke engines produce more horsepower and are much cheaper to produce than their four-stroke counterpart. Unfortunately, this increase in horsepower comes at the price of increased concentrations of pollutants in the exhaust gases. These engines have been able to continue to operate unregulated until recently. The United States Environmental Protection Agency (EPA) has begun to enforce stricter regulations for these types of engines. The design of the two-stroke engine is such that a fuel/lubricant mixture is injected into the cylinder on every stroke. This type of operation results in unused fuel, lubricant, and carbon monoxide being released in the exhaust stream into the atmosphere. For example, one chainsaw operated for two hours emits the same mass of hydrocarbon as ten 1995 model cars driven 250 miles each. Hydrocarbons are one of the many concerns the EPA has expressed about these engines. Use of traditional gasoline also means the introduction of the oxygenate methyl tert-butyl ether (MTBE) into the atmosphere. MTBE is a suspected hazard to human health and is water-soluble and therefore poses a threat to water sources. This problem tends to worsen as the engine ages. Although two-stroke engines produce more horsepower, they are significantly less efficient than four-stroke engines in terms of fuel efficiency, and they release greater amounts of environmental pollutants.

Environmentally friendly fuels such as ethanol and biodiesel are presently used in spark and compression ignited internal combustion engines. The mixing of petroleum-derived fuels with renewable fuels such as ethanol or biodiesel is a common practice and its use is expected to significantly increase in the coming years. Rifkin et al. (1983) patented Gasohol, a mixture of gasoline, ethanol, and demulsifying agent for use in a four-stroke engine. Although Gasohol left the market due in some part to public acceptance problems, the blending of ethanol into gasoline has increased in popularity based on concerns over the currently used oxygenate, MTBE. Unfortunately, gasoline/ethanol fuel cannot be used in a two-stroke engine without the A addition of a lubricating agent. It should be pointed out that heretofore all references to the use of ethanol in spark ignited two-stroke engines were in the form of a gasoline/ethanol-blended fuel and not as pure ethanol or fuel grade ethanol. This is not surprising given that traditional lubricants used in spark ignited two-stroke engines are immiscible in ethanol, and operating these engines without the lubricant would result in immediate engine failure.

Two-stroke engines can be operated using a variety of fuels such as gasoline, alcohols, ethers, and mixtures of these. Unfortunately, traditional two-stroke engine lubricants are not miscible with all of the aforementioned fuels. For example, ethanol is not miscible with petroleum derived two-stroke engine oil and cannot be used unless a suitable lubricant is mixed in with this fuel. Fuels containing other alcohols, ethers, or mixtures thereof will face the same immiscible issues.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1-Base transesterification reaction of a trialkylglyceride with methanol.

DESCRIPTION OF THE SEVERAL EMBODIMENTS

Provided is a fuel/lubricant formulation for the operation of two-stroke engines with improved emissions and performance. The fuel mixture is comprised primarily of a fuel and a lubricant. Both the fuel and lubricant are completely renewable and environmentally friendly. The fuel component of this mixture may include alcohols, ethers, ketones, gasoline, alcohol/gasoline blended fuels, nitromethane, or any combination of these fuels while the lubricant portion of the mixture includes one or more lipids, biodiesel, fatty acid alkyl esters, free fatty acids, or any combination thereof.

The composition of the lubricating fuel to be used in the engine may range from 40% to less than 100% by weight of alcohols, ethers, ketones, alcohol/gasoline blended fuels, gasoline, nitromethane, or any combination of these fuels and greater than zero to 60% by weight lipids, biodiesel, fatty acid alkyl esters, free fatty acids, or any combination thereof. These fuel/lubricant mixtures may also contain performance or compatibility enhancing compounds. Operation of two-stroke engines on these fuel/lubricant mixtures is expected to produce fewer pollutants in the exhaust.

Some of the embodiments disclosed herein will allow practitioners to blend a renewable fuel and renewable lubricant to produce a fuel/lubricant mixture for use, for example, in a two-stroke engine. For example, ethanol and biodiesel or other fatty acid alkyl esters could be blended in the following percent ranges 99-85% ethanol with 1-15% lipid, biodiesel, fatty acid methyl esters, or free fatty acids as the lubricant to produce the fuel mixture. This invention provides an environmentally friendly fuel mixture that when burned would produce much cleaner emissions than the traditional gasoline/lubricant mixtures currently used.

The inventors have found that since traditional lubricants are immiscible with most alcohols, an alcohol miscible lubricant is needed if ethanol or primary alcohols are to be the main fuel. Possible lubricants are lipids, biodiesel (traditionally vegetable oils and animal fat), other fatty acid alkyl esters, or free fatty acids. Lipids have been shown to be excellent lubricants in other applications. Biodiesel, for instance, is known to have a higher lubricity values than both petroleum diesel and Jet A-1 fuel. Some of these lubricants are completely miscible in alcohol and would provide the needed lubrication for the proper operation of the engine. There are no reports found that suggest the use of the mixture of two renewable fuels, for example ethanol and biodiesel, in an internal combustion engine. However, a similar mixture has been suggested as a replacement for fuel oil in home heating furnaces (Norton & Norton, U.S. Published Patent Application No. 2004-0194368). In this case, however, the biodiesel is used as fuel and not as a lubricating agent.

Lipids like ethanol are considered to be a negative producer of carbon dioxide since their originals are biological in nature. Lipids originate from a variety of sources such as plant, animal, and microbial. Biodiesel and other fatty acids alkyl esters are produced via the transesterification reaction of lipids (traditionally triglycerides) to produce glycerin and fatty acid methyl esters as shown in FIG. 1. Lipids are fats that are produced by all living organisms. Biodiesel is most commonly produced from vegetable oils such as soybean and rapeseed and must pass ASTM 6751 tests. Diesel engines that have been operated using neat biodiesel or petroleum-derived diesel blended with biodiesel have shown similar performance with the following exceptions. The first is the decrease in SOX and a slight increase in NO_(x) when operated using biodiesel or biodiesel blends. The second is notable decreases in engine wear when operated using neat biodiesel or biodiesel blends. The present inventors have found that biodiesel has a much better lubricity factor than petroleum-derived diesel and as a consequence extends the life of the engine.

Since ethanol performs similarly to gasoline in a spark ignited four-stroke engine, it stands to reason that it would serve as a viable substitute to gasoline in a spark ignited two-stroke engine. However two-stroke engines still require the addition of a lubricant in the fuel in order to operate. Given the improvements in diesel engine performance when operated with as little as 1% biodiesel, it is believed the same effects could be realized in a spark ignited two-stroke engine through the addition of 1% or greater biodiesel into the fuel. The inventors have found that a fuel comprised of alcohols, ethers, gasoline, ketones, alcohol/gasoline blended fuels, or any combination of these fuels with a lubricant comprised of lipid, biodiesel, fatty acid alkyl esters, or free fatty acids provide similar performance with improved emissions and engine wear. To date, four small two-stroke engines have been operated for two or more hours on a mixture of 97.5% ethanol with 2.5% biodiesel.

The embodiments disclosed herein are significantly better in terms of environmental impact because soil microorganisms would easily degrade raw product released into the environment and the emissions would not contribute to the greenhouse effect like petroleum-derived fuels and lubricants. Emissions are greatly improved through the use of environmentally friendly fuels such as renewable fuels and lubricants. The release of hydrocarbons in the exhaust could be reduced to well below the EPA's required levels. Although the lubricant in the lubricating fuel would still be introduced into the environment, it would be environmentally benign.

In one embodiment, the lubricating fuel includes a mixture comprised of 85-99% denatured ethanol or other primary alcohol as the fuel and 1-15% lipid, biodiesel, fatty acid methyl esters, or free fatty acids as the lubricant.

The lipids, fatty acid alkyl esters, and free fatty acids are distinctly different from the alkyl esters disclosed by Norton et al. which are not disclosed as components in a self-lubricating fuel. The present inventors found that combinations of these materials with ethanol provide a self-lubricating fuel. Such a fuel can be used in any internal combustion engine and are particularly well-suited to use in two-cycle engines with or without the use of additional lubricants. Further, a range of lubricating fuel compositions is available, which can also include ethers, ketone, nitromethane. etc.

The fuel may be suitably selected from one or more alcohol, gasoline, ether, ketone, nitromethane, or combination thereof. The fuel may be present in the lubricating fuel in an amount ranging from 40% to less than 100% by weight of the lubricating fuel. This range includes all values and subranges therebetween, including 40, 41, 42, 43, 44, 45, 56, 57, 48, 49, 50, 52, 54, 56, 58, 60, 65, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 95.5, 96, 96.5, 97, 97.5, 98, 98.5, 99, 99.5, and less than 100% by weight.

The alcohol may include a C₁₋₆ alcohol or a C₁ or C₃₋₆ alcohol. The alcohol may be branched or unbranched, denatured, neat, anhydrous, aqueous, fuel grade, or other alcohol. Nonlimiting examples of the alcohol include hexanol, pentanol, butanol, isobutanol, propanol, isopropanol, ethanol, methanol. Combinations of alcohols are possible. In one embodiment, the alcohol may be ethanol. In one embodiment, the fuel excludes ethanol. In one embodiment, the alcohol may include a mixture of ethanol, methanol, isopropanol and pentanol.

The gasoline may include a blended or unblended gasoline. It may be leaded or unleaded. Combinations of gasoline are possible.

In one embodiment, the fuel is a gasoline/alcohol blend, for example, gasohol. For example, the fuel may include a mixture of 90% by weight gasoline and 10% by weight ethanol.

The ether may include any volatile or inflammable ether. The ether may be an dialkyl ether, alkyl-aryl ether, or aryl-aryl ether. Some nonlimiting examples of the ether include dimethyl ether, methoxyethane, and diethyl ether. Combinations of ethers are possible.

The ketone may include any volatile or inflammable ketone. Some nonlimiting examples of ketones include acetone, butanone, and acetophenone. Combinations of ketones are possible.

In one embodiment, the fuel may include a mixture of alcohol/ether/ketone. In one embodiment, the lubricating fuel may include a mixture of alcohol/ether/ketone in combination with biodiesel.

The fuel may include nitromethane alone, or in combination with one or more of the C₁₋₆ alcohols, gasoline, ether, and/or ketone.

The lubricant may be suitably selected from one or more biodiesel, lipid, fatty acid alkyl ester, fatty acid, or combination thereof. The lubricant may be present in the lubricating fuel in an amount ranging from greater than 0% to 60% by weight of the lubricating fuel. This range includes all values and subranges therebetween, including greater than 0, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 22, 25, 27, 30, 32, 35, 37, 40, 45, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, and 60% by weight.

The lipid may include any lubricating lipid. Some nonlimiting examples of lipids include trialkylglycerol, vegetable oil, soya oil, corn oil, peanut oil, chemically oxidized oil, diakylglyceride, monoalkylglyceride, and phospholipid. Combinations of lipids are possible.

In one embodiment, the lubricating fuel may include a mixture of one or more lipids such as trialkylglycerol (for example vegetable oil, soya oil, corn oil, peanut oil, etc.) dialkylglyceride, monoalkylglyceride, and/or phospholipid, in combination with one or more alcohols. In one embodiment, the lubricating fuel may include a mixture of one or more lipids (for example trialkylglycerol, dialkylglyceride, monoalkylglyceride, and/or phospholipid) in combination with a mixture of alcohols (for example ethanol, methanol, isopropanol, and pentanol). In one embodiment, the lubricating fuel may include a mixture of one or more lipids (for example trialkylglycerol, dialkylglyceride, monoalkylglyceride, and/or phospholipid) and an alcohol/gasoline blend. In one embodiment, the lubricating fuel may include a mixture of one or more lipids (for example trialkylglycerol, dialkylglyceride, monoalkylglyceride, and/or phospholipid, etc.) in combination with a gasoline blended fuel. In one embodiment, the lubricating fuel may include a mixture of one or more lipids (for example trialkylglycerol, dialkylglyceride, monoalkylglyceride, and/or phospholipid) in combination with one or more ethers (for example dimethyl ether, methoxyethane, and/or diethyl ether). In one embodiment, the lubricating fuel may include a mixture of one or more lipids (for example trialkylglycerol, dialkylglyceride, monoalkylglyceride, and/or phospholipid) in combination with one or more ketones (for example acetone, butanone, acetophenone, etc.). In one embodiment, the lubricating fuel may include a mixture of one or more lipids (for example trialkylglycerol, dialkylglyceride, monoalkylglyceride, and/or phospholipid) in combination with an alcohol/ether/ketone mixture.

The fatty acid alkyl ester may include any lubricating fatty acid alkyl ester. Some nonlimiting examples of fatty acid alkyl ester include those having the formula RCHOOR′ wherein R is a straight chain, saturated or unsaturated C₃₋₂₁ alkyl group and R′ is a straight or branched, saturated or unsaturated C₁₋₆ alkyl group. Some examples of fatty acid alkyl ester include methyl, ethyl, propyl, butyl, pentyl, or hexyl esters of butyric, lauric, myristic, palmitic, stearic, or arachidic acid. Combinations of fatty acid alkyl esters are possible.

In one embodiment, the lubricating fuel may include a mixture of one or more fatty acid alkyl esters and one or more C₁₋₆ alcohol. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acid alkyl esters and ethanol. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acid alkyl esters and one or more alcohols other than ethanol (for example hexanol, pentanol, butanol, isobutanol, propanol, isopropanol, methanol, etc.). In one embodiment, the lubricating fuel may include a mixture of one or more fatty acid alkyl esters and a mixture of ethanol, methanol, isopropanol and pentanol. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acid alkyl esters and an alcohol/gasoline blended fuel. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acid alkyl esters and gasoline or a gasoline blended fuel. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acid alkyl esters and one or more ether. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acid alkyl esters and one or more ketone. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acid alkyl esters and an alcohol/ether/ketone mixture.

The fatty acid may include any lubricating free fatty acid. Some nonlimiting examples of fatty acid include those having the formula RCHOOH wherein R is a straight chain, saturated or unsaturated C₃₋₂₁ alkyl group. Some examples of fatty acids include butyric, lauric, myristic, palmitic, stearic, or arachidic acid. Combinations of fatty acids are possible.

In one embodiment, the lubricating fuel may include a mixture of one or more fatty acids and one or more C₁₋₆ alcohols. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acids and one or more alcohols other than ethanol (for example hexanol, pentanol, butanol, isobutanol, propanol, isopropanol, methanol, etc.). In one embodiment, the lubricating fuel may include a mixture of one or more fatty acids and a mixture of ethanol, methanol, isopropanol and pentanol). In one embodiment, the lubricating fuel may include a mixture of one or more fatty acids and an alcohol/gasoline blended fuel. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acids and one or more gasoline blended fuel. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acids and one or more ether. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acids and one or more ketone. In one embodiment, the lubricating fuel may include a mixture of one or more fatty acids and an alcohol/ether/ketone mixture.

The lubricating fuel may optionally contain one or more fuel conditioners to improve the properties of the resulting fuel mixture. Examples of these include cold flow improvement agents, ignition improvement agents, and the like. The lubricating fuel may optionally contain one or more compounds which improve engine compatibility (for example corrosion inhibiting agent, anitmicrobial agent, and the like). The lubricating fuel may optionally contain 0-40% by weight two-stroke engine oil. The lubricating fuel may optionally contain 0-40% by weight water. Mixtures are possible.

In one embodiment, nitromethane may be present as an additive, though in a smaller amount. In such an embodiment, the nitromethane is present in an amount less than 40% by weight.

In one embodiment, the lubricating fuel includes a lipid lubrication component and one or more of the following fuel components:

-   -   a) ethanol     -   b) one or more C₁ and/or C₃₋₆ alcohols (for example hexanol,         pentanol, butanol, isobutanol, propanol, isopropanol, methanol,         etc.)     -   c) gasoline     -   d) ether (for example dimethyl ether, methoxyethane, and/or         diethyl ether)     -   e) ketone (for example, acetone, butanone, and/or acetophenone)     -   f) nitromethane     -   g) or any combination thereof.

In one embodiment, the lubricating fuel in the preceding paragraph additionally comprises a fatty acid alkyl ester. In one embodiment, the lubricating fuel in the preceding paragraph additionally comprises a free fatty acid.

In one embodiment, the lubricating fuel includes an alkyl ester lubrication component and one or more of the following fuel components:

-   -   a) ether (for example dimethyl ether, methoxyethane, and/or         diethyl ether)     -   b) ketones (for example, acetone, butanone, and/or acetophenone)     -   c) nitromethane     -   d) or any combination thereof.

Suitable applications include both small and large engines. In small engines, such as string trimmers, chain saws, leaf blowers, lawn mowers, etc., the lubricating fuel could be sold in prepackaged gallon/s quantities. In larger engines, such as outboard motors, personal water crafts, all terrain vehicles, motorcycles, cars, etc., the lubricating fuel could be sold through metered pumps.

It should be clear that, upon review of this disclosure, wherein the claimed subject matter is fully described, the skilled artisan may recognize alternative embodiments, equivalents and obvious improvements to the specific embodiments disclosed herein; and these alternative embodiments, equivalents and obvious improvements, though not specifically disclosed herein, are similarly encompassed by the claims. It should also be clear that the Abstract is provided only to enable the reader to quickly determine from a cursory inspection the nature and gist of the technical disclosure, and is not intended to be limiting. 

1. A method, comprising: operating a two-stroke engine with a lubricating fuel, the lubricating fuel comprising: at least one fuel selected from the group consisting of C₁₋₆ alcohol, gasoline, ether, ketone, nitromethane, and a mixture thereof; and at least one lubricant selected from the group consisting of biodiesel, lipid, fatty acid alkyl ester, fatty acid, and a mixture thereof.
 2. The method of claim 1, wherein the fuel is C₁₋₆ alcohol or a mixture comprising C₁₋₆ alcohol and one or more of gasoline, ether, ketone or nitromethane.
 3. The method of claim 1, wherein the fuel is ethanol.
 4. The method of claim 1, wherein the fuel is gasoline or a mixture comprising gasoline and one or more of C₁₋₆ alcohol, ether, ketone or nitromethane.
 5. The method of claim 1, wherein the fuel is ether or a mixture comprising ether and one or more of C₁₋₆ alcohol, gasoline, ketone or nitromethane.
 6. The method of claim 1, wherein the fuel is ketone or a mixture comprising ketone and one or more of C₁₋₆ alcohol, gasoline, ether, or nitromethane.
 7. The method of claim 1, wherein the fuel is nitromethane or a mixture comprising nitromethane and one or more of C₁₋₆ alcohol, gasoline, ether or ketone.
 8. The method of claim 1, wherein the fuel is present in the lubricating fuel in an amount of 40% to less than 100% by weight.
 9. The method of claim 1, wherein the lubricant is biodiesel or a mixture comprising biodiesel and one or more of lipid, fatty acid alkyl ester or fatty acid.
 10. The method of claim 1, wherein the lubricant is lipid or a mixture comprising lipid and one or more of at least one lubricant selected from the group consisting of biodiesel, fatty acid alkyl ester or fatty acid.
 11. The method of claim 1, wherein the lubricant is fatty acid alkyl ester or a mixture comprising fatty acid alkyl ester and one or more of biodiesel, lipid or fatty acid.
 12. The method of claim 1, wherein the lubricant is fatty acid or a mixture comprising fatty acid and one or more of biodiesel, lipid or fatty acid alkyl ester.
 13. The method of claim 1, wherein the lubricant is present in the lubricating fuel in an amount of greater than zero to 60% by weight.
 14. The method of claim 1, wherein the two-stroke engine is a spark-ignited two-stroke engine.
 15. The method of claim 1, wherein the two-stroke engine is a compression-ignited two-stroke engine.
 16. The method of claim 1, wherein the lubricating fuel further comprises at least one selected from the group consisting of a cold flow improvement agent, an ignition improvement agent, a corrosion inhibiting agent, an antimicrobial agent, water, two-stroke engine oil, and a mixture thereof.
 17. A lubricating fuel, comprising: at least one fuel selected from the group consisting of C₁ alcohol, C₃₋₆ alcohol, gasoline, ether, ketone, nitromethane, and a mixture thereof; and at least one lubricant selected from the group consisting of biodiesel, lipid, fatty acid alkyl ester, fatty acid, and a mixture thereof.
 18. The lubricating fuel of claim 17, wherein the lubricating fuel is suitable for operating a two-stroke engine.
 19. The lubricating fuel of claim 17, wherein the fuel is present in an amount of 40% to less than 100% by weight.
 20. The lubricating fuel of claim 17, wherein the lubricant is present in an amount of greater than zero to 60% by weight.
 21. The lubricating fuel of claim 17, further comprising at least one selected from the group consisting of a cold flow improvement agent, an ignition improvement agent, a corrosion inhibiting agent, an antimicrobial agent, water, two-stroke engine oil, and a mixture thereof.
 22. A method, comprising operating a two-stroke engine with the lubricating fuel of claim
 17. 23. A lubricating fuel, comprising: at least one fuel selected from the group consisting of C₁₋₆ alcohol, gasoline, ether, ketone, nitromethane, and a mixture thereof; and at least one lubricant selected from the group consisting of lipid, fatty acid, and a mixture thereof.
 24. The lubricating fuel of claim 23, wherein the lubricating fuel is suitable for operating a two-stroke engine.
 25. The lubricating fuel of claim 23, wherein the fuel is present in an amount of 40% to less than 100% by weight.
 26. The lubricating fuel of claim 23, wherein the lubricant is present in an amount of greater than zero to 60% by weight.
 27. The lubricating fuel of claim 23, further comprising at least one selected from the group consisting of a cold flow improvement agent, an ignition improvement agent, a corrosion inhibiting agent, an antimicrobial agent, water, two-stroke engine oil, and a mixture thereof.
 28. A method, comprising operating a two-stroke engine with the lubricating fuel of claim
 23. 